Sprint drive

cthia wrote:

Jonathan_S wrote:Could you add one to a normal Mk23? Certainly it seems you could replace the current 3rd drive with one; but that would actually reduce it's powered range and terminal velocity just to get more delta-v in the final 75 seconds of flight. That's probably not worth it.

Adding a 4th drive would require a larger missile (like the system defense missiles) or you'd have to pull a lot of other things out, and there's not much that could be downsized except # of laserhead and size of warhead. So even if you could cut those enough to squeeze a 4th drive into a missile of the same dimentions the reduction in damage doesn't seem worth the extra range and terminal velocity...

So basically I don't see it as worth while for the RMN to incorporate into their shipboard MDMs - and definitely not into their DDMs.

I'm not quite too sure about that Jonathan.

If the RMN could pull off at least a "sprint mode" made to work in conjunction with staggered missile launches, taking advantage of the weakness of point defense, I think would have an even bigger impact on its already devastating effect.

A sprint mode that kicks in right after the Dazzlers and Dragon's teeth spin up?

[snip]

I always thought it was a waste, for end of run missiles to complete their runs, with copious amounts of drive time left on tap. Can we utilize all of the remaining drive time in an all out burst?

I'm not sure it can be done. But I'm certainly sure of its proposed effectiveness, if used correctly.

Jonathan_S wrote:Missile drive definitely can't use up their remaining time in an all out burst. That totally contradicts everything about how RFC set up missile drives to work. You can set their accel, but then they run until they burn out or you cut power. Either way you can't restart them. They'll almost always have "wasted" time at the end of run.


However, I went back and did some number crunching on a notional Mk23 that replaced the 3rd drive with a Mk31/Viper derived one (130,000 gees for 75 seconds) and got numbers that surprised me. I'd thought, based on the Cataphract, that the shorter duration of the Sprint drive would make the missile slower across the final 2 million km CM zone, but on a 3 drive missile the numbers don't support that. (Which I guess is why it's good to number crunch multiple scenarios)

As well there's an outside chance the higher acceleration might confuse a poorly programmed tactical computer, but honestly any computer updated to deal with the 0.8+c closing speeds of MDMs shouldn't have much issue tracking sprint mode drive. And any computer, like the SLN's current ones, already incapably of handling that closing speed can hardly be much less useful against a Sprint drive. But still, even without tac computers rejecting the missile as impossible, the better terminal acceleration could still help.


First, continuous powered range, with the stock Mk23 on the normal 9 minute half-power profile; these are terminal burnout numbers.
Stock - 540 seconds, 65,726,640 km, 0.81 c
Sprint - 435 seconds, 44,966,565 km, 0.86 c

Now some specific ranges. I'm picking a flight profile to minimize flight time, so at shorter ranges some drives may be high (H), some half power (L), the final sprint (S), and if necessary to make range a ballistic (B) segments. I won't list out all the details, but the summarized flight profile will be listed.

Code: Select all

Range  |    Conventional    |      Sprint
16m km | HHBH 192.9s 0.541c | HHS  182.2s 0.641c
32m km | HHL  293.3s 0.621c | HLS  312.7s 0.765c
48m km | HLL  409.3s 0.706c | HLBS 430.5s 0.770c
64m km | LLL  532.9s 0.801c | LLBS 552.3s 0.860c
72m km | LLBL 578.7s 0.812c | LLBS 601.6s 0.860c


I didn't explicitly calculate the time to cover the last 2 million km, but in all cases the missile is already under Sprint drive and given the better terminal velocities it's got to be quicker.

On the other hand beyond 45 million km, were the Sprint equipped MDM has to coast to make range the total flight time of the conventional MDM is lower, despite the slower terminal velocity. However even though that means the enemy could potentially blow up ships still controlling your initial missile salvo, being less than 30 seconds from impact the missiles should do pretty well on their own (a non-Apollo MDM would already be on it's own just due to lag, but Apollo round trip lag at 72 million km is under 8 seconds).

Weird Harold wrote:

Maldorian wrote:Maybe I wrote my post not clear enough or you are misunderstanding me:

"I am NOT talking about the Cataphracts! I am talking about the Sprint Drive technology and if it is useful for manty missles."

If you're talking about the "Sprint Drive" the MAlign puts on its dispatch boats and other starships, that is useless on missiles because that is a Hyper-generator rather than an improved impeller drive. It is called "Sprint" because it allows a ship to reach higher hyper bands -- with consequent decrease in travel time in hyperspace.

If you're talking about a "Sprint Drive" on a missile, Cataphracts are the only missiles currently employed by any combatant that has a CM-derived second stage drive. If you're talking about the missiles provided the PNE for the attack on Torch, you're talking about Cataphracts.

The System Defense variant of Apollo aside, Manticoran missiles already have more advantages than pure speed in the final stage and speed alone can be compensated for with software upgrades.

What would be far more useful, IMHO, would be a final drive with "infinitely variable speed" so the defensive systems don't have a simple "binary" choice of speeds for aiming prediction. If defenses actually have to measure the speed of incoming missiles, rather than simply identifying the missile type and selecting from "fast" or "slow" it would delay response fractionally and complicate computation of lead-angle.

cthia wrote:
First things first. Excellent number crunching! We appreciate the extra mile.

Here's the thing, pursuant to the holes in my understanding...

The tracking computers begin tracking from launch, giving them plenty of time to lock on. At the moment a "sprint mode" would kick in, the distances would be much shorter and the swivel mechanism of point defense has to re-seek for the burst of acceleration. There has to be a seek time, if given in milliseconds, it is much too slow.

Consider, the difference in "seek times" of movable disk drives (also given in ms) where the platter head has to seek for the information requested by physically moving across the media.

Granted, a software that can handle .81c should have no problem tracking .86c. However, that tracking represents a smooth acceleration which began quite a distance away. Sprint mode drives will offer a whole new bag of squirming worms that isn't as straight forward as tracking faster missiles. Sprint mode activated at such a close angle of attack would not be a trivial thing for the "hardware" that the "software" controls. It would be interesting to test in theory anyways.

Also, if used in conjunction with Manty ECM, amidst the haze of dazzlers and dragon's teeth, a sprint mode would be devastating. Though I wonder if the false signatures created by Manty ECM could duplicate false sprint mode drives.

Jonathan_S wrote:

cthia wrote:
First things first. Excellent number crunching! We appreciate the extra mile.

Here's the thing, pursuant to the holes in my understanding...

The tracking computers begin tracking from launch, giving them plenty of time to lock on. At the moment a "sprint mode" would kick in, the distances would be much shorter and the swivel mechanism of point defense has to re-seek for the burst of acceleration. There has to be a seek time, if given in milliseconds, it is much too slow.

Consider, the difference in "seek times" of movable disk drives (also given in ms) where the platter head has to seek for the information requested by physically moving across the media.

Granted, a software that can handle .81c should have no problem tracking .86c. However, that tracking represents a smooth acceleration which began quite a distance away. Sprint mode drives will offer a whole new bag of squirming worms that isn't as straight forward as tracking faster missiles. Sprint mode activated at such a close angle of attack would not be a trivial thing for the "hardware" that the "software" controls. It would be interesting to test in theory anyways.

Also, if used in conjunction with Manty ECM, amidst the haze of dazzlers and dragon's teeth, a sprint mode would be devastating. Though I wonder if the false signatures created by Manty ECM could duplicate false sprint mode drives.

The Sprint drive's we've seen are 75 second endurance and one based of the Mk31/Viper would kick on as far out as 15 million km. That's lots of time for a tracking computer to adjust to the higher acceleration and prepare CMs and PDLCs.

I guess you could wait until entering PDLC range, but on a 3 drive missile saving your final drive that late would require a much slower approach and spending more time, at lower velocity, crossing the 2 million km wide CM zone just to have a chance to try to head-fake the PDLC.

I think that's most likely a bad trade-off. Most MDMs get picked of by CMs, so increasing your vulnerability to CMs in an attempt to decrease your vulnerability to the less effective PDCLs doesn't seem ideal. Alternatively you could light if off at 3-4 million km off to try to screw up the initial CM interception. Still from there it'd take even that drive 3-5 seconds to cross the CM and PDLC zones, so there'd still be time to adjust any follow-on CM and the PDLC shot.




The (larger) 4 drive system defense MDM could do that though, they've still got the 0.8c closing speed even before firing off their final CM drive. On them it's much harder to figure out when it makes the most sense to light off the CM based final drive.

cthia wrote:

Weird Harold wrote:What would be far more useful, IMHO, would be a final drive with "infinitely variable speed" so the defensive systems don't have a simple "binary" choice of speeds for aiming prediction. If defenses actually have to measure the speed of incoming missiles, rather than simply identifying the missile type and selecting from "fast" or "slow" it would delay response fractionally and complicate computation of lead-angle.

Do pardon my boldness.

Quite an interesting concept Harold. And that would be quite the capable little missile that could.

Is there any textev regarding the "guestimation" used in point defense? I wouldn't think that was the case. Guessing (aiming prediction) at location would represent an intentional injection of uncertainty into the tactic. That doesn't sound "survivable" to me, and would seem to go against the notion of "lock on." Besides, against Manty missiles, such a concept wouldn't work, as the software would need to know the moment the missile's sprint mode activated. If lost amidst ECM, that's a forgone conclusion.

cthia wrote:

Weird Harold wrote:What would be far more useful, IMHO, would be a final drive with "infinitely variable speed" so the defensive systems don't have a simple "binary" choice of speeds for aiming prediction. If defenses actually have to measure the speed of incoming missiles, rather than simply identifying the missile type and selecting from "fast" or "slow" it would delay response fractionally and complicate computation of lead-angle.

Do pardon my boldness.

Quite an interesting concept Harold. And that would be quite the capable little missile that could.

Is there any textev regarding the "guestimation" used in point defense? I wouldn't think that was the case. Guessing (aiming prediction) at location would represent an intentional injection of uncertainty into the tactic. That doesn't sound "survivable" to me, and would seem to go against the notion of "lock on." Besides, against Manty missiles, such a concept wouldn't work, as the software would need to know the moment the missile's sprint mode activated. If lost amidst ECM, that's a forgone conclusion.

Weird Harold wrote:No textev required, the principle is as old as trying for lunch with the first rock thrown at a bird.

In terms of the Honorverse, there's no no light-speed sensor that can directly detect an incoming missile in time to intercept it, so they are restricted to what can be determined by tracking the missile wedge and any emissions the missile might put out.

Computing a lead angle for a constant speed and course is trivial; allowing for a static set of known accelerations for a possible second stage is also trivial.

Computing a lead angle for a target that is randomly making minor changes in course is more difficult. Throw in random variations in acceleration/speed and computing a lead angle becomes very difficult. Honorverse missiles can vary their course but they can't vary their acceleration/speed. Even a few G's of acceleration change should throw off interception computations if anyone could figure out how to do it with missile drives.

In modern terms it's called "Jinking" to avoid SAM or AA missiles, and the ASG-22 Lead Computing Optical Sight mounted in the F-4(D) Phantoms I spent my career working on didn't even try for that level of prediction. (1960's vintage analog lead computer.)

Maldorian wrote:Maybe I overread it, but the point with Sprint drives is: A faster missle cross the enemy defense line faster give the enemy less time to fight it. The most people here are thinking of single missles. In Honorverse they fire them in dozen, hundred and thousand packages.

I don´t know how long a missle stay in the defense line and if you can reload your Counter missle tubes in the middle of a wave, but if the missles are faster, the laser cluster could fight less missles. More missles arrive, more damage.

cthia wrote:Our sling and rock works because we always have the bird in sight. And the bird does not have a burst of acceleration or ECM to cause us to temporarily lose sight.

cthia wrote: In the Honorverse, tracking = sight. Tracking, sights missile at .81c. We time our rock for .81c. Sprint mode activates. Oops.

Weird Harold wrote:No textev required, the principle is as old as trying for lunch with the first rock thrown at a bird.

In terms of the Honorverse, there's no no light-speed sensor that can directly detect an incoming missile in time to intercept it, so they are restricted to what can be determined by tracking the missile wedge and any emissions the missile might put out.

Computing a lead angle for a constant speed and course is trivial; allowing for a static set of known accelerations for a possible second stage is also trivial.

Computing a lead angle for a target that is randomly making minor changes in course is more difficult. Throw in random variations in acceleration/speed and computing a lead angle becomes very difficult. Honorverse missiles can vary their course but they can't vary their acceleration/speed. Even a few G's of acceleration change should throw off interception computations if anyone could figure out how to do it with missile drives.

In modern terms it's called "Jinking" to avoid SAM or AA missiles, and the ASG-22 Lead Computing Optical Sight mounted in the F-4(D) Phantoms I spent my career working on didn't even try for that level of prediction. (1960's vintage analog lead computer.)